1. Technical Field
The present invention refers to a lead-frame for semiconductor devices, particularly during the encapsulation operation of the devices.
2. Description of the Related Art
During the molding process of a semiconductor device or an integrated circuit, this is welded to a metal structure or frame called “lead-frame,” and has fine blades usually made of copper, or other conductive material for the electric connection.
During a successive phase a mold, the so-called “package,” is closed around the integrated circuit by the upper and lower surfaces of the lead-frame and the mold is filled, by injecting means, with some plastic or resinous material, so as to make the body of the integrated circuit package, after the resin has solidified.
The mold has “air vents,” so that it can be completely filled with the plastic material in such a way that air bubbles are prevented from forming inside the plastic material which would prevent the mold from being completely filled.
The air vents are designed to let out the air present in the mold to avoid residuals or flashes, nevertheless the presence of these air vents permits small quantities of resinous material to seep out on the lead-frame external to the mold, resin which forms the so-called “flashes.”
The flashes of resinous material are very fragile, possess a weak cohesion with the surface of the lead-frame, and therefore can be easily removed from the lead-frame itself.
The detachment of the flashes from the lead-frame causes a series of problems, for example, that the resin which has become detached can go onto the sensors of the machinery used in phases successive to the molding, causing undesired halting of the machinery itself with evident degradation of performance and production losses.
Another very important problem occurs during the phase of separation of the integrated circuits from the lead-frame. In fact because of this operation the flashes, which fall and adhere to the terminals (the so-called leads) of the lead-frame, can be treated as contaminating elements and thus entail negative results to the electric tests and also refusal of material by the client.